Arsonium halides

Arsonium Ylides. Arsonium ylides were first prepared by reaction between an arsonium halide and phenyUithium. Thus methyitriphenyiarsonium iodide [1499-33-8], C H gAsI, and phenyUithium give tripbenylarsonium metbylide [19365-61-8], C H yAs ... 

Numerous tetrahedral halogeno complexes [T1" X4] (X = Cl, Br, I) have been prepared by reaction of quaternary ammonium or arsonium halides on TIX3 in nonaqueous solution, and octahedral complexes TI "X< ] (X = Cl, Br) are also well established. The binuclear complex Cs3[Tl2"Cl<)J is an important structural type which features two TlCls octahedra sharing a common face of 3 bridging Cl atoms (Fig. 7.9) the same binuclear complex structure is retained when Tl " is replaced by Ti ", V ", Cr " and Fe " and also in K3W2CIS and CssBiily, etc. 

Aryl tellurium halides combine with phosphonium halides, arsonium halides, or ammonium pseudohalides to produce aryl(dihalo)tellurates(II) or aryl(dipseudohalo) tellurates(II). 

Aryl tellurium trihalides accept halide ions from tropylium bromide, ammonium halides, phosphonium halides, arsonium halides, sulfonium chlorides, telluronium chlorides, and diphenyl iodonium chloride to form aryltetrahalotellurates(lV)1-5. 

The reactions of alkali metal, ammonium, phosphonium, or arsonium halides with diorgano tellurium dihalides produce diorganotrihalotellurates or diorgano tetra-halotellurates1,2 (page 668). 

X-ray and spectroscopic studies indicate that the arsonium halides are ionic. Mc4AsBr consists of tetrahedral Mc4As+ units and separate bromide ions. X-ray structures have also been obtained on a series of tetraphenylarsonium salts. " A regular tetrahedral stmcture is found about the arsenic atom when the counterion is a halide or ion of similar size. However, as the size of the counterion increases, the crystals become more disordered. In solution, tetraphenylarsonium salts are almost completely dissociated, but ion pairing can be significant and is dependent primarily on the dielectric constant of the solution. 

Quaternary arsonium halides may also be obtained from the corresponding hydroxides by treating the latter with halogen adds ... 

There is considerable evidence for this type of reaction in organoarsenic chemistry and, indeed dissociation-equilibrium was believed to be the cause of racemization of arsonium halides which, for synthetic reasons, usually contained at least one alkyl substituent (often" the benzyl group) on the arsenic atom. In 1939, fractional crystallization was achieved of the diastereomers of the diarsonium picrate 3 . The individual diastereo-mers of the salt, racemic (R, R ) and meso (R, S ), were stable in boiling ethanol, a fact that should have dispelled concerns of dissociation equilibria in halide-free arsonium salts. In 1940, the tetrahedral structure of [AsPh4]I was established by X-ray crystallography. ... 

Arsinimines are hydrolysed by aqueous base ° or acid °, to triphenylarsine oxide and an amide. With hydrogen chloride they form arsonium halides ... 

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